CALGARY — The company behind the proposed Trans Mountain pipeline expansion has dropped a request that the National Energy Board allow it to conduct some construction activity on the multi-billion dollar project.

Last week, lawyers representing Kinder Morgan Canada subsidiary Trans Mountain asked the board for permission to install mats to deter fish spawning after the board told it last month to stop doing so.

The lawyers said if the request was not granted, construction on the $7.4-billion project could be delayed by a year.

Lawyer Terri-Lee Oleniuk at Osler, Hoskin & Harcourt has now written to the NEB saying the window for “safely and effectively” installing the mats has passed and the company is withdrawing the request.

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The board told the company to stop installing the deterrent mats because they're considered construction activity, and the company does not yet have all conditions approved for pipeline construction.

Oleniuk says in a letter issued Friday that Trans Mountain intends to remove the existing mats and notes that doing so while the fish are spawning could constitute serious harm under the Fisheries Act.

First Nations, environmentalists and the B.C. government have expressed opposition to the project, which would nearly triple the capacity of the pipeline running from Edmonton to Burnaby, B.C., saying the expansion could have serious implications for the environment.